EARLY DEVOXIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 149 



Diaphorostoma ventricosum (Conrad) 



Diaphorostoma affine (Billings) 



Diaphorostoma desmatum Clarke 



Diaphorostoma pereeense nov. 



Plate 15, figures 17-23 



Pla t y o s t o m a V e n t r i c o s a Conrad Jour. Acad. Nat. Sci. Phila. 1842. 8:275, 



pi. 17. fig. 5 

 Platyostonia ventricosa Hall. Palaeontology of New York. 1859. 3:300, 



pi. 55, fig. 9 

 Platyostonia aft in is Billings. Palaeozoic Fossils. 1874. v. 2, pt i, p. 60, 



pl- 5. fig- 2 

 Diaphorostoma desmatum Clarke. N. Y. State Mus. Mem. 3. 1900. p. 29, 



pl- 3, fig- 13-19 



The names above cited apparently express definite local values, more or 

 less combined in the New York Oriskany shells but differentiated in the 

 Gaspe faunas. Diaphorostoma ventricosum (Oriskany of New 

 York), if restricted to the large shells with expanded whorls and broad 

 stomata, is variable in the hight of its spire, and this feature is shown by 

 Hall's figures. Perhaps the degree of elevation never attains that presented 

 by Billings's D. affine (Grande Greve), which is based upon this differ- 

 ential. If this difference is applied to the larger Gaspe shells it will serve 

 as a valid basis of distinction. The large shells very abundant in the Perce 

 Rock have uniformly depressed spire, the apex of which is generally not 

 above the upper plane of the body whorl. Diaphorostoma d e s m a- 

 t u m was based on smaller shells from the Becraft mountain Oriskany, with 

 a highly developed cancellated surface and relatively narrow body whorl. 

 There is little doubt that these do not represent an early growth condition 

 of D. ventricosum for large specimens of the latter obtained from 

 Glenerie near Kingston, N. Y., show, on the early whorls, sharp concentric 

 striae without revolving lines. Typical examples of D. desmatum are 

 frequent at Grande Greve, while the large form called D. affine is quite 

 rare. The shells at Perce fail to show at any stage these peculiarities of 

 surface, the sculpture consisting of fine compressed concentric striations. 



The differentials, then, in these shells are as follows : 

 D. ventricosum; large, with body whorl greatly expanded, flattened on 



the periphery ; spire usually low, never depressed, 

 sometimes moderately elevated. Surface with sharp 

 concentric lines on early whorls ; in mature whorls 

 these lines are confluent and obscure. Union Springs, 

 Oriskany Falls, Glenerie, Becraft mountain, Grande 

 Greve (?) etc. 



